This invention relates to a process of combusting an H.sub.2 S-containing feed gas with oxygen and air in at least one burner, which opens into a combustion chamber, to produce a gas mixture which contains H.sub.2 S and SO.sub.2 and is intended to be converted to sulfur by the Claus process, wherein the combustion chamber is supplied with oxygen through the central tube of the burner, with the H.sub.2 S-containing feed gas through at least one second tube, which coaxially surrounds the central tube, and with air through a coaxial outer tube.
Such a process and related equipment have been described in German Patent 34 30 015. In that known process, relatively low temperatures and low velocities of flow of the gases are maintained adjacent to the outlet of the burner.